Of the morbidities resultant to breast cancer (BrCa) treatment, lymphedema is one of the most feared and prevalent with an estimated 2-400,000 diagnosed cases in the U.S. Increased ann size resultant to lymphedema may cause decreased range of motion and function, decreased muscle strength, and alters activities of daily living. Survivors may find lymphedema more distressing than mastectomy as it is less possible hide the physical manifestation and loss of arm function. Strength training is an intriguing intervention for BrCa survivors, as there is evidence exercise improves health parameters, quality of life and symptoms of arm morbidity. However, despite a lack of prospective scientific research to indicate such exercise puts BrCa survivors at risk for lymphedema, current clinical guidelines advise against participating in vigorous upper body exercise, and in particular, lifting objects that weigh more than 5 to 15 pounds. These restrictions greatly limit activities in which survivors may participate, which then negatively impacts health, function and quality of life. Strength training allows women to gradually increase strength in a controlled setting, making it less likely that the occasional activities of daily living that require strenuous upper body work (shoveling snow, carrying children) would over-stress the lymphatic system. This proposal stems from compelling preliminary data from a 6 month randomized controlled trial of progressive twice-weekly strength training in 81 recent BrCa survivors; in the treatment group, there was no onset of lymphedema or worsening of symptoms in women who had been previously diagnosed with lymphedema.. These data, combined with other reports in the literature, support this proposal of a randomized controlled trial to evaluate the effects of twice-weekly progressive strength training on lymphedema symptoms and physiology of the lymphatic system, as well as quality of life parameters, compared to a non-exercising control goup. We will recruit 288 survivors (144 with lymphedema. 144 without lymphedema) 5-15 years post-BrCa diagnosis to participate in this randomized controlled exercise intervention consisting of 2 groups (n= 144 per group). Randomization will occur within lymphedema status. The knowledge gained from this study may impact recommendations for therapeutic regimens, participation in activities of daily living, and recommendations for exercise for health promotion in BrCa survivors.